Rethinking Mobile Backhaul Offering for a Fixed Operator like Colt

© 2012 Colt Telecom Group Limited. All rights reserved.

Rethinking mobile backhaul offering for a fixed operator like Colt

Valéry Augais

Strategy and Architecture

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Contents

1 Moving from the traditional «transparent» to a managed

services approach

2 Off-loading MNO’s RAN with small cells: implications

for the fixed operator

3 Reviewing the key service and technical attributes

that will forge the design: L2/L3, X2, security,

synchronisation and C-RAN

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Colt – Europe’s information delivery platform

• 43,000km EU high capacity long distance

network, 27,000km transatlantic

• Connecting 22 countries, 39 metro

networks and >150 cities

• 20 data centres and 19,000 connected

buildings

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From the traditional «transparent» offer…

Various successful 3G backhaul trials and deployments

• Ethernet Virtual Private Line over fibre and copper (EFM DSL) access

– Multiple point to point EVCs, single multiplexed Ethernet UNI

• No hop-by-hop timing (SyncE/BC/TC) but OTT 1588 and on-site GPS

– High jitter performance in the backhaul

mobile core

L2 CPE

backhaul MNO mobile core MNO cell sites

NB

L2 edge

L2 access &

aggregation

RNC 1588 GM 1588 slave

GPS

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to managed services

• Fast pace evolving radio access technologies (esp. LTE-A as of 3GPP R10)

– Improved latency (CoMP)

– More accurate time synchronisation (MIMO, CoMP, TD-LTE, eMBMS)

– Small cells

• Resulting likely new and more stringent MNO requirements in areas such as

– Latency (esp. inter-eNB)

– Synchronisation (time, accuracy level)

– Heterogeneous Networks (e.g. macro vs. metro/small cells)

– But also connectivity model, security, Cloud RAN, etc.

Managed solution approach to fulfill the

anticipated diversity of MNOs’ requirements

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The small cell case

Our understanding why it matters MNO operators

• Bandwidth explosion with video & data consumption and smartphone adoption

• Insufficient capacity of 3G RAN networks organised in macro cells to support LTE

and LTE-A

– Need for complementary support of 3G cellular and Wi-Fi

• Utmost importance of traffic offload at cell spectrum level

– Frequency band re-farming on its way but long and incomplete process

– Femto cell (indoor) similarly good but incomplete

• Other rather secondary benefits with cell backhaul offload and coverage

extension

«By 2015 small cells forecast to represent more than 80% of deployed cell»

«97.5% of MNOs viewing small cells key for the future of mobile networks»

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The neutral host approach

Colt’s small cell strategy in a nutshell

• MNOs’ needs to build new backhaul for these many brand new cells

• Colt’s unique presence in Europe with dense fibre capillarity within 39 main

cities

• Colt as a leading and trusted transactional business supplier to fixed and

mobile operators

• Well established contacts between Colt and city councils & street furniture

owners

Multi-MNO neutral host small cell offer comprising:

• site access (power included) through partnerships

• backhaul connectivity (in-house)

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Small cell connectivity options

Another important piece of the puzzle to solve

• Fibre as the preferred medium when available

– Colt own fibre plant not passing nearby

– No FTTx wholesale offer

• Copper DSL as the next wireline candidate but

– Shortfall of bandwidth with currently allowed EFM options (5.7Mbps/pair)

– Highly fragmented regulations in EU for enhanced DSL modulations (EFM, VDSL2,

vectoring)

• Wireless showing more and more potentials with rapid turn-up and high capacity

(e.g. unlicensed V band) but

– LoS condition and small cell in urban environment apparently somewhat contradictory

– Questionable radio reliability and bandwidth performance in NLoS condition

Along with power supply, connectivity build likely represents another

challenge to overcome and is likely to make use of multiple media

PoE

MNO #1

MNO #2 Colt backhaul

power fibre

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Backhaul service attributes

• Multiple attributes leading to diverse requirements hence different backhaul

design variants

• Interestingly some objectives, if really required, likely to trigger a complete

revisit of backhaul design and MNO operating model

Attribute Remark

L2 or L3 connectivity Each has its supporters

Fast X2 interface For CoMP support

Security IPSec_as_a_service not high in the list though

Synchronisation Fixed operator participation with on-path

Cloud RAN To help with signalling/BW storm and fast X2

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Network layer 2-3 integration

In-flight multi-work stream programme

• Ethernet, IP and optical layers

• CPE, edge and core areas

L2 access &

aggregation

L2 service

L2 service

L2 CPE

L2 CPE

L2/L3 packet optical core

L2/L3 edge

L3 service

L3 features moving to the PE layer

IP services over Ethernet access (metro)

Ethernet services (metro & inter-metro)

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E-Line for S1

E-LAN (w/ L2 CPE) for X2

High level reference connectivity model

Evolved Packet Core

L2 CPE


small cell/eNB

L2 access &

aggregation

S-GW / MME

L2/L3 edge

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E-Line for S1

L3 VPN (w/ L2 CPE) for X2

High level reference connectivity model

Evolved Packet Core

L2 CPE


small cell/eNB

L2 access &

aggregation

S-GW / MME

L2/L3 edge

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Transitioning to fast X2

• High pressure on backhaul performance with emerging LTE-A’s X2

requirement (CoMP in 3GPP release 11)

– Very short maximum inter-eNB delay (5ms, 1ms or other) as the next 3GPP standard

requirement to support seamless HO

• Fast X2 presumably in scope of HO between macro and small cells

– Small cell to small cell less likely to happen before long

• Lower field performance of 10ms, 15ms or even more possibly acceptable for

MNOs despite impact on radio spectrum efficiency gain

• X2 marginally deployed today with base LTE but expected to increase with

more users in mobility

Centralised edge architectures uncertain to meet fast X2 objectives

Change to distributed edge to increase backhaul & mobile operators’ costs

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Adding security

Evolved Packet Core

L2 CPE


small cell/eNB

L2 access &

aggregation

S-GW / MME

L2/L3 edge

IPSec GW

E-Line for S1


IPSec tunnel initiation

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Adding security

Evolved Packet Core

L2 CPE


small cell/eNB

L2 access &

aggregation

S-GW / MME

L2/L3 edge

IPSec GW

E-Line for S1


IPSec tunnel initiation

Unbalanced security with secure S1 but unsecure X2?

Hybrid operation with complex management of key exchange certificate?

IPSec tunnel initiation on L2 CPE?

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Synchronisation requirement

• Will accurate time (needed for CoMP, etc.) turn real at some point?

• Will transparent backhaul continue to do the job?

• Will MNOs accept backhaul operators’ PRC clock synchronise the backhaul?

L2 CPE

small cell/eNB

L2 access &

aggregation

1588 GM 1588 slave

GPS L2/L3 edge

S-GW

MME

Evolved Packet Core


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Synchronisation requirement

• Will accurate time (needed for CoMP, etc.) turn real at some point?

• Will transparent backhaul continue to do the job?

• Will MNOs accept backhaul operators’ PRC clock synchronise the backhaul?

L2 CPE

small cell/eNB

L2 access &

aggregation

1588 GM 1588 slave

GPS L2/L3 edge

S-GW

MME

Evolved Packet Core


On-path synchronisation delivery with IEEE 1588v2 BC/TC support

No absolute need for physical layer synchronisation support, i.e. SyncE

Multi-clock capable devices if no PRC clock outsourcing

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Cloud RAN evolution

• C-RAN development motivated for multiple reasons

– Opex & capex cost reduction (small cell), signalling & BW storm and fast X2 (CoMP)

• Stringent requirements with current approach based on CPRI interface long-lining

– Multi-Gbps bandwidth and 0.1ms latency

EPC

L2 CPE

packet backhaul MNO super macro

cell sites (BBU pools)

super eNB

L2 access &

aggregation

L2/L3 edge

S-GW

MME

small cell/eNB

fibre and

L1 Ethernet

CPRI backhaul MNO cell sites MNO

mobile core

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Cloud RAN evolution

• C-RAN development motivated for multiple reasons

– Opex & capex cost reduction (small cell), signalling & BW storm and fast X2 (CoMP)

• Stringent requirements with current approach based on CPRI interface long-lining

– Multi-Gbps bandwidth and 0.1ms latency

EPC

L2 CPE

packet backhaul MNO super macro

cell sites (BBU pools)

super eNB

L2 access &

aggregation

L2/L3 edge

S-GW

MME

small cell/eNB

fibre and

L1 Ethernet

CPRI backhaul MNO cell sites MNO

mobile core

Alternative approach of long-lining L1-L2 radio

interface far more appealing for backhaul operators:

• Packet backhaul

• Lower bandwidth

• Longer latency

• Centralised hosting in data centres

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Summary

• 3GPP R10 being introduced now in some parts of the world (e.g. NA)

– 2-3 more years likely to go to see R11 live and with the highly demanding CoMP

in operation (especially in the lagging EU)

– Roll out of pre-CoMP small cells anticipated to happen before in ca. 2014

• No one size backhaul fits all but many multi-degree variants instead

– Radio access technologies (3G/LTE/LTE-A cellular, Wi-Fi)

– Backhaul medium (fixed, wireless)

– Other key attributes (L2/L3, latency, security, synchronisation)

High focus on backhaul and small cell business at Colt

Presently at business development and partnership stage

Detailed design and engineering level discussions to start

Rethinking Mobile Backhaul Offering for a Fixed Operator like Colt

Technology

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